Developing a new source of water resources has surfaced as an urgent facing problem due to recent serious pollution of water quality environments and water shortage. Researches on the pollution of water quality environments aim for high-quality residential and industrial water, and treatment of various domestic sewage and industrial wastewater, and interests in water treatment processes using a separation membrane having an advantage of energy saving has been rising. In addition, accelerated reinforcement on environment regulations is expected to advance wide utilization of separation membrane technologies. Traditional water treatment processes are difficult to satisfy the tightened regulations, however, separation membrane technologies secure excellent treatment efficiency and stable treatment, therefore, are expected to become a leading technology in the field of water treatment in the future.
Liquid separation is divided into microfiltration, ultrafiltration, nanofiltration, reverse osmosis, stannizing, active transport, electrodialysis, and the like, depending on the pore of the membrane.
Specifically, typical examples of such a water treatment membrane include a polyamide-based water treatment membrane, and the polyamide-based water treatment membrane is manufactured using a method in which a fine porous support is formed by forming a polysulfone layer on nonwoven fabric, and this fine porous support is immersed in an aqueous m-phenylenediamine (mPD) solution to form an mPD layer, and this mPD layer brings in contact with trimesoyl chloride (TMC) by being immersed in or coated on a TMC organic solvent, and is interfacial polymerized to form a polyamide active layer. According to the manufacturing method described above, a non-polar solvent and a polar solvent are in contact with each other, and polymerization occurs only at the interface, and as a result, a polyamide active layer having a very small thickness is formed.
Meanwhile, there is a qualification for a polyamide-based water treatment membrane to be commercially used, and it is having superior capabilities as a separation membrane such as high salt rejection and permeate flow. Salt rejection of a separation membrane commercially required is at least 97% or greater for brackish water, and an ability to have a relatively large amount of water passing through under a relatively low pressure, that is, a high flow property is required.
Meanwhile, such a water treatment membrane needs to have high salt rejection in order to be commercially used and desalinate in large quantities, and needs to have an excellent permeate flow property capable of passing excess water through even under a relatively low pressure. Accordingly, technology development for further enhancing salt rejection and permeate flow properties of a water treatment membrane has been required.
In addition, in existing polyamide-based water treatment membranes, pores of the active layer shrink when the separation membrane is re-dried, which causes a problem of significant decreases in salt rejection and permeate flow. Accordingly, in existing technologies, separation membranes have been manufactured in conditions immersed in a storage solution after being washed for removing unreacted materials and washed in DIW without re-drying the polyamide-based water treatment membrane. However, the separation membrane in a wet state has problems in that a process is inconvenient during a modulation process, and transporting costs are high.